diff --git a/docs/MobileApp.md b/docs/MobileApp.md
index 75ab2ee7..7fac8c3b 100644
--- a/docs/MobileApp.md
+++ b/docs/MobileApp.md
@@ -210,6 +210,14 @@ expo-router strips the scheme and tries to match `/private/var/mobile/…` as an
 
 The fix is a catch-all `+not-found.tsx` route (see `mobile/app/+not-found.tsx`).  When expo-router cannot match the path, it renders this screen instead.  The screen detects that the path is a filesystem path rather than a real in-app route, adds the file directly to `ShareContext`, and redirects to the Upload tab.  `UploadScreen` picks up the pending file and begins uploading automatically.  The `Linking` listener in the root layout may also fire for the same URL; `ShareContext.addPendingFile` deduplicates by URI so the file is only uploaded once.
 
+##### File accessibility and local caching
+
+Shared files may reference paths outside the app's sandbox or use security-scoped URLs that React Native's `fetch` cannot read directly.  To guarantee reliable uploads:
+
+- **`LSSupportsOpeningDocumentsInPlace`** is set to `false` in `app.json`, which tells iOS to copy shared files into the app's `Documents/Inbox` directory before handing them to the app.
+- **`UploadScreen`** uses `expo-file-system` (`FileSystem.copyAsync`) to copy any `file://` URI that is outside the app's cache/documents directory to a local cache path before uploading.  This ensures the file is readable regardless of its origin.
+- **MIME type inference**: Both `+not-found.tsx` and the `Linking` handler in `_layout.tsx` infer the MIME type from the file extension (e.g. `.pdf` → `application/pdf`) so the server receives a correct `Content-Type` instead of `application/octet-stream`.
+
 ##### iOS Action / Share Extension (future enhancement)
 
 Apps like DeepL ("Translate in DeepL") and Microsoft Word ("Convert to Word") appear as **Action Extensions** in the iOS share sheet — a system-level feature that requires a separate Xcode target built with Swift or Objective-C.  A proper Action Extension runs in its own process and must share authentication credentials with the main app via an iOS **App Group** (shared keychain / shared container).
diff --git a/mobile/app.json b/mobile/app.json
index 1e3ef852..0e755fed 100644
--- a/mobile/app.json
+++ b/mobile/app.json
@@ -24,7 +24,7 @@
         "NSPhotoLibraryAddUsageDescription": "DocuElevate saves scanned documents to your photo library.",
         "UIBackgroundModes": ["remote-notification"],
         "ITSAppUsesNonExemptEncryption": false,
-        "LSSupportsOpeningDocumentsInPlace": true,
+        "LSSupportsOpeningDocumentsInPlace": false,
         "CFBundleDocumentTypes": [
           {
             "CFBundleTypeName": "All Documents",
diff --git a/mobile/src/screens/UploadScreen.tsx b/mobile/src/screens/UploadScreen.tsx
index ea3ae1e6..d883dd5c 100644
--- a/mobile/src/screens/UploadScreen.tsx
+++ b/mobile/src/screens/UploadScreen.tsx
@@ -14,6 +14,7 @@
 
 import { Ionicons } from "@expo/vector-icons";
 import * as DocumentPicker from "expo-document-picker";
+import * as FileSystem from "expo-file-system";
 import * as ImagePicker from "expo-image-picker";
 import React, { useCallback, useEffect, useRef, useState } from "react";
 import {
@@ -66,12 +67,47 @@ export default function UploadScreen() {
   // Core helpers (declared before the effects that depend on them)
   // ---------------------------------------------------------------------------
 
+  /**
+   * Ensure a file URI is accessible for upload.
+   *
+   * Files received via the iOS Share Sheet / "Open In…" may reference paths
+   * outside the app's sandbox or use security-scoped URLs that React Native's
+   * fetch cannot read directly.  This helper copies such files to the app's
+   * cache directory so the upload can proceed reliably.
+   *
+   * URIs from expo-image-picker and expo-document-picker are already in the
+   * app's cache and are returned unchanged.
+   */
+  const ensureLocalUri = useCallback(async (uri: string, filename: string): Promise<string> => {
+    // Android content:// URIs are handled natively by React Native's fetch.
+    if (!uri.startsWith("file://")) return uri;
+
+    // Files already in the app's cache or documents directory are accessible.
+    const cacheDir = FileSystem.cacheDirectory;
+    const docDir = FileSystem.documentDirectory;
+    if (cacheDir && uri.startsWith(cacheDir)) return uri;
+    if (docDir && uri.startsWith(docDir)) return uri;
+
+    // External file (e.g. from iOS Inbox or security-scoped URL) – copy to
+    // cache so the upload has guaranteed read access.
+    const safeName = filename.replace(/[^a-zA-Z0-9._-]/g, "_");
+    const destUri = `${cacheDir}shared_${Date.now()}_${safeName}`;
+    try {
+      await FileSystem.copyAsync({ from: uri, to: destUri });
+      return destUri;
+    } catch {
+      // Copy failed – fall back to the original URI (might work for some paths).
+      return uri;
+    }
+  }, []);
+
   const uploadFile = useCallback(async (uri: string, filename: string, mimeType?: string) => {
     const id = `${Date.now()}-${filename}`;
     setUploads((prev) => [{ id, filename, status: "uploading", uri, mimeType }, ...prev]);
 
     try {
-      const resp = await api.uploadFile(uri, filename, mimeType);
+      const localUri = await ensureLocalUri(uri, filename);
+      const resp = await api.uploadFile(localUri, filename, mimeType);
       setUploads((prev) =>
         prev.map((item) =>
           item.id === id
@@ -85,7 +121,7 @@ export default function UploadScreen() {
         prev.map((item) => (item.id === id ? { ...item, status: "error", error: msg } : item))
       );
     }
-  }, []);
+  }, [ensureLocalUri]);
 
   const retryUpload = useCallback(async (item: UploadItem) => {
     if (!item.uri) return;
@@ -100,7 +136,8 @@ export default function UploadScreen() {
     );
 
     try {
-      const resp = await api.uploadFile(item.uri, item.filename, item.mimeType);
+      const localUri = await ensureLocalUri(item.uri, item.filename);
+      const resp = await api.uploadFile(localUri, item.filename, item.mimeType);
       setUploads((prev) =>
         prev.map((u) =>
           u.id === item.id
@@ -114,7 +151,7 @@ export default function UploadScreen() {
         prev.map((u) => (u.id === item.id ? { ...u, status: "error", error: msg } : u))
       );
     }
-  }, []);
+  }, [ensureLocalUri]);
 
   // ---------------------------------------------------------------------------
   // Polling – check server-side processing status every 5 seconds